Why does the student go to see the professor? What goal for his class does the professor mention?

Listen to a conversation between a student and her creative writing professor. (S = Student, P = Professor)
S: I’ve had lots of trouble with the assignment you gave us. You know, to write a short memoir. I started like a thousand times. And every time I feel like it’s terrible.
P: I’m gonna let you in on a little secret. Whenever I give an autobiographical assignment, the majority of my students are totally fine with it and can go on forever, in fact. But if a few, like yourself, hesitate at the idea of having to write about themselves…
S: At least I’m not alone. So do you think that maybe I could write a short biography of someone else instead?
P: Oh, no. That won’t work. I’d rather you turn in what you thought was a poor paper about yourself than a brilliant one about someone else.
S: You mean it’s okay if I do a mediocre job?
P: I really don’t think that’s going to be a problem for you. You know, it’s not bad for writers to be pushed out of their comfort zones. And it may help to remember that my main goal is to get people to experiment with different genres. The effort you put forth will be apparent in the work and that will help determine your grade.
S: Yeah. But I’m still not comfortable with the idea of turning in something I’m not super proud of. And there’s also the length issue. How could I possibly sum up my whole 18 years in 15 pages or less?
P: I think you’re confusing memoir with autobiography.
S: They are not the same?
P: Technically, no. Though the terms are often used interchangeably, generally, autobiographies chronicle the author’s life from his or her earliest memories to the present. Memoirs tend not to be so broad. They are more thematic. Take Katharine Graham, the former publisher of The Washington Post. She wrote a prize-winning autobiography that goes from the early years to her retirement. If she had to set out to write a memoir, she might’ve focused on, say, her newspaper’s coverage of the Nixon presidency, or she could’ve concentrated on her childhood, or even a single memorable event and how it shaped her values.
S: Oh, I see. Well, when I was ten, my family moved to a different town. Then two years later just as I was settling in with many friends, we moved again. And I need to start all over. But then last fall when I moved into the dorms here on campus, making friends wasn’t a problem. I wasn’t even nervous. And I’m sure that was due to those early experiences.
P: What a perfect theme for your memoir!
S: You think?
P: Definitely. Just take what you told me. And just flesh out with some anecdotes and develop your insights a bit more.